Motor brake control



Oct. 21, 1952 w, GRQEN 2,615,153

MOTOR BRAKE CONTROL Filed May 12 1951 INVENTOR. WILLEM GROEN M MM ATT'YS Patented Oct. 21, 1952 MOTOR BRAKE CONTROL Willem Groen, Chicago, Ill., assignor to Onsrud Machine Works, Inc., Chicago, 111., a, corporation of Illinois Application May 12, 1951, Serial No. 226,005

1 Claim. 1

This invention relates to brake mechanism. for the control of motors, particularly such as are equipped for driving milling cutters and the like, in which momentum of rotating parts is an important factor to be quickly overcome to bring the parts to rest.

The main objects of this invention are to provide an improved control means for applying a friction brake and having timing mechanism adapted to automatically release the brake after it has brought the motor to rest; to provide an improved mechanism of this kind in which the braking eifect is adjustable so as to terminate the braking eifect approximately in harmony with the expenditure of the momentum of the moving parts; to provide improved pneumatic brake setting means that operates automatically and requires the attention of an operator merely for a minimum of time to initiate the braking operation, as for example, by the mere pressing of a control button; and. to provide motor brake mechanism of this kind capable of being controlled manually or by electrical circuit means of thestart-stop, push-button station type.

A specific embodiment of this invention is illustrated schematically in the accompanying drawing in which:

Figure 1 is a fragmentary side elevation, partly in section, of an electric motor having a power shaft equipped with friction brake mechanism of the general type shown in the patent of Rudolph Onsrud No.2,379,099 issued June 26,1945, but equipped for pneumatic operation with control mechanism in accordance with the present invention.

Fig. 2 shows an electric circuit including a start-stop, push-button station arranged for supplying current to the motor and for actuating the brake control mechanism when the stop button is pushed for breaking the electric circuit to the motor.

The power shaft l is driven by the motor 2 and has a brake disk 3 made fast thereon by a key 4 and held in place by a nut 5 on the shaft. A ring-shaped brake shoe 8, preferably of wood and comprising an annular series of segments, is carried by a brake head I forming part of a lever pivoted to the motor frame at 8 on one side of the head and having a hand lever 9 at the opposite side for direct manual application of the brake. A compression spring l0, mounted on studs II and i2, normally urges the brake head 1 and shoe 6 away from engagement with the disk 3.

In the form shown, the control mechanism of the present invention having a plunger It in position to bear on the brakehead I and having a range of movement corresponding to the desired movement of the brake head I for applying and releasing the brake pressure of the shoe 6 on the disk 3. The cylinder .l3, may be carried by a bracket I5 on the motor frame. i

In thelform shown, the plunger is actuated by air-pressure. The plunger; l4 travels in the chamber 16 of the cylinder l3 and is of sufficient transverse area to apply an. appropriate pressureagainstthe brake head 1 to overcome the momentum of the rotating motor and the parts driven thereby, so as to stopthe same rapidly. Air pressure is supplied by a pipe I! connected to an appropriate source and is con trolled by a spring-closed valve 48 that maybe opened by pressing the button 19 against th action of the spring 20.- 3

In addition to the manual control indicated by the button IS, the valve i8 is controlled by magnetic means such as a solenoid 21 of the electric circuit shown in Fig. 2.

In the form shown the electric circuit, which is a 3-phase circuit, comprises line conductors 22, 23 and 24 connected to the motor 2 by a main magnetic starter 25 which is normally urged by a spring or gravity to its open position and which is controlled by a push button station. including a starting switch button 26 and a stop switch button 21, connected in series. The starting switch 26 is normally opened and the stop switch 21 is normally closed, as indicated in Fig. 2, and a holding circuit 28 shunts the starting switch.

On closing the starting switch 26 by pressing the start button, the solenoid 29 is activated to close the magnetic starter 25 through the circuit that comprises conductors 30, 3| and 32, assuming that the pressure switch 33 is closed. The switch 33 is held closed by pressure in the air supply line 34 when that pressure is sufficient to operate the brake control mechanism and is otherwise spring opened to prevent starting of the motor 2. Closing of the magnetic starter 25 closes the holding circuit 28 through a holding switch 35 which is operated simultaneously with the main switch by the solenoid 29.

When the switch 21 is opened by pressing the stop button, the holding circuit which comprises pressure switch 33 and conductors 28, 3| and 32 is opened and the starter solenoid 29 is de-energized to open the starter and break the line circomprlses a cylinder 13 3 cult to the motor 2. Upon opening this holding circuit, the inward movement of switch member 21 closes a third circuit, comprising conductors 30, 36, 31 and 38, and contacts 21.! causing the solenoid 2| to open valve l8 and allow a charge of air under pressure to enter the chamber I6 of the brake actuating cylinder 13 by way of the pipe l1.

As soon as the stop button 21 is released, the stop switch returns to its normal position as shown in Fig. 2, thus breaking the last-named circuit and permitting the supply valve I8 to close.

The cylinder I3 has a bleeder port 39 which allows a gradual escape of air or other elastic fluid from the chamber it. This bleeder port is reguated by a needle valve 40 so as to time the escape of the air from the chamber 16, resulting in a gradual release of the pressure of the brake shoe 6 upon the disk 3 under the action of spring I2 in such manner that the brake shoe will release the disk 3 at approximately the same time that the shaft l comes to rest as a result of the braking action.

It is apparent that by cutting off the current to the motor and holding the valve !8 open, either by pressure on the button [9 or on the stop button 27, the air pressure can be held at maximum effect until after the shaft I has been brought to rest.

However, in the operation of large milling machines, the saving of the operator's time is a matter of very great importance. The present invention reduces the operator's required attention for stopping the machine to the mere act of depressing and instantly releasing the stop button 21, whereupon the motor circuit is automatically opened and the brake is applied and in turn released as soon as the rotation of the shaft ceases. Under normal conditions, the adjustment of the needle valve 40 is such that the momentum of the shaft 1 and its attachments would be overcome just before the braking pressure of the brake shoe is entirely released.

Although but one specific embodiment of this invention is herein shown and described, it is understood that numerous details of the construction shown may be altered or omitted without departing from the spirit of the invention, as defined in the following claim:

I claim:

The combination of a motor shaft, brake mechanism normally inactive for resisting rotation of Said shaft, a pneumatic cylinder and piston positioned to apply braking pressure to said brake mechanism, means for supplying elastic fluid under pressure to said cylinder, a normally closed valve controlling the admission of said fluid to said cylinder, a bleeder port leading from said cylinder for timing the escape of such fluid pressure from said cylinder, and electrical control means comprising a main motor circuit, a normally open main switch controlling said motor circuit, a holding circuit, magnetic means in said holding circuit for closing said main switch, a normally open switch in said holding circuit arranged to be held closed by the pressure of said elastic fluid supply, a third circuit having manetic means for opening said fluid supply valve. and a start-stop station having a normally open start switch for activating said holding circuit and said station having a normally closed stop switch adapted to open said holding circuit and simultaneously close said third circuit.

WILL-EM GROEN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,264,299 Hellrnund Apr. 30, 1918 2,013,665 Messier Sept. 10, 1935 2,382,263 Schnell Aug. 14, 1945 2,525,461 Schnell Oct. 10, 1950 FOREIGN PATENTS Number Country Date 120,330 Great Britain Nov. 7, 1918 

